Art of producing pigments by electrolysis.



PATENTED NOV. 19. 1907.

.E. D. CHAPLIN.

ART OF PRODUCING PIGMENTS BY BLBGTROLYSIS.

APPLICATION FILED FEB. 3, 1906.

WITIJESSIS Jan nix .o. enptrtix, or nos'iox, MASSMJHU ART OF PRODUCING PIGIVIENTS BY ELECTROLYSIS.

Specification of Letters Patent.

tied Nov. 19, 190?.

Application tiled lclnnarv 3.1906- Scrial No. 399.238.;

To all whom it may concern:

citizen of the United States, and a resident of l soluble salts of lead in the olectr ilyzer for 55 Be it known that. l, EDWIN l). (n.tPLtX, a t

Boston, in the county of Suffolk and State of more particularly to a process for so produci tallio lead in the presence of a soluble sal ing lead clnontate.

in the manufacture of lead rhromate by electrolysis, I prefer to employ an electro lyte. which under the intluti-nce of the electric current. will separate into a solvent of lead and an alkaline hydrate and thereby to pro duce in the anode ctnnpartmcnt containing metallic lead, which may be the anode of the electrolyzer, av solution of a soluble salt of lead, and in the cathode conmartment, an alkaline hydrate l have found it essential to the commercial iroduction of lead chromate to maintain the lead solution and the alkaline hydrate separate and not to prot'luee atiylead precipitate in the elcctrolyzer itself. I have also found it essential to employ some means, such as an oxidizing agent, to prc vent the formation of insoluble salts of lead in the electrolyzer.

As clearly set out in Letters Patent No. 555,232 and 563,553, granted t A. B. Browne and myself, and indiettta-s Patent 'No. 675,555 grantcd to ll. G. Ilallloran and 'myselt, for processes of producing lead car bonate by electrolysis, certain insoluble basic salts of lead are formed in the electrolyzcr, thereby rendering the processes untaken in order to prevent such formation.

The object of the present invention is to provide a process of producing lead chromate b Y electrolysis in which the formation of inso 11bit. basic salts of lead in the FltC trolyzer may be prevented by any means suitable for the pur )osc. While the formation of the aforesai basic lead salts may be prevented in a variety of ways, I prefer in the process herein set forth, to render such formation impossible by electrolytically proexample, a soluble chlorid salt or an oxidizing agent such as a soluble chlorate of an alkaline base.

.111 letters Patent No. 538,998, granted to A. ll. Browne and myself is described a process of producing lead chromate by electrolysis, to which reference maybe had for a more complete disclosure of the principles involved in the present application than is necessary to set forth herein.

My invention may best be understood by having reference 1 o the drawing which accomi panics and forms a part of this specification, and which illustrates in diagrammatic form fan arrangement of apparatus and circuits ducing a soluble acid salt of lead obtained,

preferably, by electrolytically dissolving mel. capable of preventing the formation of innitrate and sodium chlorid. commercial, unless certain pretaiutrons are 1 whereby my process may be carried into etfect but it is to be understood that my in vcntion is broader than mere apparatus and may be carried into etl'ect by a great variety of apparatus and circuit arrangements.

in the drawing the iigure represents an apparat us and syst cm of circuits for electrolytically producing lead chroniate.

in the figure. 1 represents a supply tank, containing an electrolyte, which under the 'intlucnce of the electric current, will be separated into an alkaline hydrate and a solvent of lead. such for exampleas an aqueous solution of a non-alkaline salt, preferably sodium nitrate, and containing also an aqueous solution of a soluble chlorid or chlorate salt, which may be a chlorid or a chlorate of an alkaline base, preferably sodium chlorid or chlorate. .i shall hereinafter refer to the'solution in tank 1 as the neutral solution and shall assume that, it consists of sodium 3 represents an electrolyzer divided into an anode compartment 3 and a cathode compartment 3, by means of the foraminous diaphragms 4 -'1-, between which is formed a compartment for receiving the electrolyte from the tank 1 through the pipe .2, which is provided with a valve 2'. 1 01" the purpose of preventing a mixture of the anolyte and eatholyte in the electrolyzer, i: may maintain a preponderance of pressure on the inner sides of said diaphragms, preferably by maintaining the level of the electrolyte between the diaphragms higher than the level of the anolyte and catholyte. The level of the electrolyte in the compartmentbetween the diaphragms is indicated by the dotted in the two portions of each of said pipes.

The lead to be operated upon is placed in the anode compartment and may form the anode of the electrolyzer. In the present case the lead'is shown the form of a lead pig 5, connected by the cou'ductor d to the positive pole of the dynamo D, or other suit able source of current. The cathode 6 of the electrolyzer may consist of copper or any other suitable metal, and is connected by the so conductor 0 to the negative pole of the dynamo. VVhen' the electrolyzer. is charged with the neutral solution and the electric current passed therethrough, a soluble acid salt of lead. is formed in theanode compartment 3 and an alkaline hydrate, in the present case assumed above, sodium hydrate, is

formed in the cathode compartment 3".

Presumably lead nitrate is,at first formed in the anode compartment and this, by the acts tion of the sodium chlorid and under the influence of the electric current, is converted into lead chlorid, which is soluble at the temperature at which the electrolyte is maintained by the steam coil 30, or by any other as suitable means, and, finally by the continued action of the current, the lead chlorid is conyerted into lead oxychlorid, which is soluble at ordinary temperatures. The lead oxychlorid being an acid salt of lead, renders impossible the formation of insoluble basic salts of lead; The lead oxychlorid or soluble acid salt of load so formed in the anode compartment 3 is drawn off by the pipe 8" into the settlin tank 9 and the alkaline hydrate tonne in the cathode com artment 3" is drawn oil by the pi e 7 into t e settlin tank 11'. By means of t e pipe 10, rovide with, a valve 10 the acid salt of le is discharged from the tank 9 into the precipitating tank 23, or as is obvious, it may be discharged into said precipitating tank 23 directly from the anode compartment 3.

In the' precipitating tank 23 the acid salt of lead may be converted intolead chromate by treating it with any suitable chromateor bichromate, or mixture of the two, such for example, as a mixture of sodium or potassium chromate and bichromate, an aqueous solution of which may be contained in the tank '28 and discharged into the precipitating tank by" the pipe 29.- The resulting lead chromate settlesat the bottom of the tank 23 upon the filter 24,}vhile the filtrate, which is substantially the original neutral solution,

is pumped back to the supply tanh l hil'the pump 27 through the pipe 26 provided with the valve 26. The lead chromatcmay be withdrawn by the pipe 25, washed, and dried for use. The alkaline hydrate which in the present case is assumed to be sodium hydrate, may be carbonated by passing carbon- 12, into the tank 13 and mix therewith a so-- lution of chrome alum contained in the tank 14 and drawn off int0 the tank 13 by the pipe 15 provided with a valve 15. By proucing an excess of sodium hydrate, i pres cipitate and redissolve chrome hydrate in the tank 13 and convey such solution of chrome hydrate into the electrolyzer 17 through the pipe 16 provided with the valve 16. A solution of sodium chlorid is conveyed from the tank 18 by the pipe 19, provided with the-valve 19, into the electrolyzer 17 and under the influence of the electric current from the dynamo D the poles of which are connected by the wires (1 and b, respectively, to the electrodes 21 and 22, of the cell 17, a suitable mixture of sodium c'hromate and bichromate is produced from the mixture ofochrome hydrate and sodium chlorid. This mixture is then conveyed from the cell 17 by the pipe 20, provided with the valve 20, into the tank 23, where it precipitates lead chromate from the solution of the acid salt of lead discharged into said tank by the pipe 10.

claim: 1. As an improvement in theart of producing lead chromate by electrolysis, the

process herein described which consists electrolytically reducing from metallic lead a soluble acid sa t of lead and converting said soluble acid salt of lead into lead chrpmat.

2. As an improvement in the art of producing lead chromate by electrolysis, the process herein described which consists in electrolytically dissolving metallic leadin the presence of a soluble chlorid salt, converting the resulting lead chlorid into lead oxychlorid, hnd producing leadchromate from said lead oxychlorid.

3. As an improvement in the art of producing lead chromate by electrolysis, the

process herein described which consists in electrolytically dissolving metallic lead in the presence of a soluble chlorid of an alkal ne base, thereby producing an alkaline hydrate and leadchlorid, converting said lead In testimony whereof, I havenhereunto chlorid. into lead oxychlorid, wlthdrawin subscribed my name this fifth day of Jan. 10

said alkaline'hydrate and lead oxychlorid 1906. l

into separate receptacles, electrolytically pro- T 5 dlicing amixture of chromate and bichro-. EDWD OHAPLIN' mate of an alkaline base from said alkaline Witnesses: hydrate, and treating said lead oxychlorid CHARLES C(KURTZ,

with s aid mixture to produce lead chromate. GEO. YWOQDVWGRTHQ, 

